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| author | James Montgomery <james_montgomery@disroot.org> | 2026-07-03 15:26:41 -0400 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2026-07-09 19:43:04 -0500 |
| commit | 7ee526883dc555fb95d5f12306da464dc7d96c83 (patch) | |
| tree | 156bcc6824f51db915fa75414d95fcac2e191968 /fs/smb | |
| parent | 4396059945ca7f0258385f5f8d77392046ce7bf1 (diff) | |
| download | linux-next-7ee526883dc555fb95d5f12306da464dc7d96c83.tar.gz linux-next-7ee526883dc555fb95d5f12306da464dc7d96c83.zip | |
ksmbd: defer destroy_previous_session() until after NTLM authentication
In ntlm_authenticate(), destroy_previous_session() is called using a
user pointer resolved from the client-supplied NTLM blob username field
before the NTLMv2 response is validated. An authenticated attacker can
set the NTLM blob username to match a victim account and set
PreviousSessionId to the victim's session ID; destroy_previous_session()
destroys the victim's session while ksmbd_decode_ntlmssp_auth_blob()
subsequently rejects the request with -EPERM.
Move destroy_previous_session() and the prev_id assignment to after
ksmbd_decode_ntlmssp_auth_blob() returns success and use sess->user
rather than the pre-authentication lookup result. This matches the
ordering already used by krb5_authenticate(), where
destroy_previous_session() is called only after
ksmbd_krb5_authenticate() returns success.
Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-cifs/20260702155449.3639773-1-james_montgomery@disroot.org/
Signed-off-by: James Montgomery <james_montgomery@disroot.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/smb')
| -rw-r--r-- | fs/smb/server/smb2pdu.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c index b73167785e87..f5fc3ad671a1 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -1717,11 +1717,6 @@ static int ntlm_authenticate(struct ksmbd_work *work, return -EPERM; } - /* Check for previous session */ - prev_id = le64_to_cpu(req->PreviousSessionId); - if (prev_id && prev_id != sess->id) - destroy_previous_session(conn, user, prev_id); - if (sess->state == SMB2_SESSION_VALID) { /* * Reuse session if anonymous try to connect @@ -1761,6 +1756,10 @@ static int ntlm_authenticate(struct ksmbd_work *work, } } + prev_id = le64_to_cpu(req->PreviousSessionId); + if (prev_id && prev_id != sess->id) + destroy_previous_session(conn, sess->user, prev_id); + /* * If session state is SMB2_SESSION_VALID, We can assume * that it is reauthentication. And the user/password |